Heretofore, the most common form of attaching cable and electrical metal tubing (EMT) to electrical junction boxes is by the use of an interior-threaded lock nut which is screwed onto the exterior-threaded electrical fitting that extends into the junction box.
The disadvantage of the common threaded type of electrical connector is that it requires the use of both hands to secure it in place in the junction box. The flexible cable or EMT with the connector attached must be held in one hand while the threaded lock nut is held in the other hand, matched up to the threaded barrel of the connector, and then turned clockwise with respect to the connector until the lock nut is secured tightly to the connector. Matching the threaded lock nut to the connector can be very difficult, especially when the electrical junction box is in a location that is difficult to reach, such as a junction box for an overhead light fixture. In situations such as this, when it is difficult to see or to reach the junction box, it is very difficult to match up the connector and the lock nut and start the lock nut on the connector.